PSI - Issue 37

Alessandro Zanarini et al. / Procedia Structural Integrity 37 (2022) 525–532

531

7

A. Zanarini / Structural Integrity Procedia 00 (2021) 1–8

Shakers:active #1[2611] mute #2[931] Risk-index mapping PINK NOISE excit. max= 1 [mN]

Shakers:active #1[2611] mute #2[931] Risk-index mapping PINK NOISE excit. max= 1 [mN]

Real part [/] [projection angle 0 deg] Dof [725]

Real part [/] [projection angle 0 deg] Dof [2105]

ESPI_r [725] = -2.317e+00

ESPI_r [2105] = 2.315e+01

5.588e+01 ESPI_r -1.481e+01

5.588e+01 ESPI_r -1.481e+01

(c) ALESSANDRO ZANARINI @ TU-Wien, Austria Marie Curie FP7-PEOPLE-IEF-2011 PIEF-GA-2011-298543 Project TEFFMA - Towards Experimental Full Field Modal Analysis

(c) ALESSANDRO ZANARINI @ TU-Wien, Austria Marie Curie FP7-PEOPLE-IEF-2011 PIEF-GA-2011-298543 Project TEFFMA - Towards Experimental Full Field Modal Analysis

a

b

Fig. 7. Examples of Risk Index mapping in dof 725 in a and 2105 in b , with pink noise excitation from shaker 1. If threshold = 10, a defect in dof 725 is tolerable, whereas a defect in dof 2105 is intolerable, thus dangerous.

are completely di ff erent due to the lower emphasis on higher frequency contributions, the location of the enquiry dof can tell when it is located in a more or less dangerous zone, compared to the chosen threshold in Eq.8. This to underline the e ff ectiveness of full-field FRF based Risk Index mapping : it was su ffi cient to change the dynamic signature of the excitation to understand how the problematic areas on the sample changed. The damage location assessment on real components may play a relevant role under the defect tolerance strategies . The chosen 2 dofs above were just a virtual example, but the same ESPI-based NDT shown in paper Zanarini (2021a) may give us a real defect distribution map , which can be the input in Risk Index maps , here obtained by ESPI full field dynamic testing in Zanarini (2021b), both for production & exercise of our parts. In this coupled strategy, the real location of the defect can tell if it can be accepted or not, in manufacturing or exercise, once the real structural dynamics and excitation signature are fully known. Therefore the NDT , the structural dynamics’ measurement and the defect tolerance criteria can all be based on full-field dynamic testing , to put the most advanced experimental structural dynamics’ knowledge into higher safety targets. Many activities were run before being able to pursue the final goal of a methodologically sound risk tolerance assessment . Among them, it’s important to recall: the extended tests to acquire high quality full-field FRFs for NVH & advanced design procedures; the accurate evaluation of Strain FRF maps from experimental full-field receptances ; the evaluation of Stress & Von Mises equivalent stress FRF maps with proper constitutive models; the simulation of Von Mises PSDs directly from experimental full-field FRFs and coloured noise excitation ; the fatigue life predictions by means of spectral methods , with full-field impedance-based experimental models ; and the definition of a Risk Index to discriminate the dangerous location of defects, once the real dynamic behaviour is fully retained and not simplified. It is now possible to state that the experimental optical full-field measurement techniques are becoming mature & reliable for a risk tolerance assessment in production and working conditions, because of their ability to identify defects and to retain a refined structural dynamics in both the frequency and spatial domain, directly from real samples and without any FE model to be carefully updated. 6. Conclusions

Acknowledgements

The European Commission Research Executive Agency is acknowledged for funding the project TEFFMA - To wards Experimental Full Field Modal Analysis, funded by the European Commission at the Technische Universitaet Wien, Austria, through the Marie Curie FP7-PEOPLE-IEF-2011 PIEF-GA-2011-298543 grant in years 2013-2015.